U.S. patent number 9,634,532 [Application Number 14/150,100] was granted by the patent office on 2017-04-25 for inertial drive actuator.
This patent grant is currently assigned to OLYMPUS CORPORATION. The grantee listed for this patent is OLYMPUS CORPORATION. Invention is credited to Masaya Takahashi.
United States Patent |
9,634,532 |
Takahashi |
April 25, 2017 |
Inertial drive actuator
Abstract
An inertial drive actuator includes a shift unit that generates
a shift in a first direction and in a second direction opposite to
the first direction, a base plate that moves with the shift of the
shift unit, and a mover disposed on a surface of the base plate and
having a magnetic field generating unit. The mover has a first yoke
that guides magnetic flux generated by the magnetic field
generating unit such that the magnetic flux concentrates on a
surface of the mover facing the base plate with respect to both S
and N poles. Also included is a second yoke provided on a side of
the base plate facing away from the mover. The frictional force
acting between the mover and the base plate is controlled by
controlling a magnetic field generated by the magnetic field
generating unit to drive the mover.
Inventors: |
Takahashi; Masaya (Hachioji,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
OLYMPUS CORPORATION |
Tokyo |
N/A |
JP |
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Assignee: |
OLYMPUS CORPORATION (Tokyo,
JP)
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Family
ID: |
47506028 |
Appl.
No.: |
14/150,100 |
Filed: |
January 8, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140183982 A1 |
Jul 3, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2012/067297 |
Jul 6, 2012 |
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Foreign Application Priority Data
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Jul 8, 2011 [JP] |
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2011-151809 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K
1/34 (20130101); H02N 2/025 (20130101) |
Current International
Class: |
H02K
1/34 (20060101); H02N 2/02 (20060101) |
Field of
Search: |
;310/329,328,323.02
;74/99R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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01-138975 |
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May 1989 |
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JP |
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04-000273 |
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Jan 1992 |
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JP |
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06292374 |
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Oct 1994 |
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JP |
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H10-257786 |
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Sep 1998 |
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JP |
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11-69847 |
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Mar 1999 |
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JP |
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11136979 |
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May 1999 |
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JP |
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2007129821 |
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May 2007 |
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JP |
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2007-288828 |
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Nov 2007 |
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JP |
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2008072438 |
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Mar 2008 |
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JP |
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2009-177974 |
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Aug 2009 |
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JP |
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2009273253 |
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Nov 2009 |
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JP |
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5185640 |
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Apr 2013 |
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JP |
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2011055427 |
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May 2011 |
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WO |
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Other References
Extended Supplementary European Search Report dated Mar. 23, 2015
from related European Application No. 12 81 1901.3. cited by
applicant .
International Preliminary Report on Patentability dated Jan. 23,
2014 from related International Application No. PCT/JP2012/067297,
together with an English language translation. cited by applicant
.
International Search Report dated Oct. 2, 2012 issued in
PCT/JP2012/067297. cited by applicant.
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Primary Examiner: Ismail; Shawki S
Assistant Examiner: Gordon; Bryan
Attorney, Agent or Firm: Scully, Scott, Murphy &
Presser, P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a continuation of PCT/JP2012/067297,
filed on Jul. 6, 2012, which is based upon and claims the benefit
of priority from Japanese Patent Application No. 2011-151809, filed
on Jul. 8, 2011, the entire contents of each of which are
incorporated herein by reference.
Claims
What is claimed is:
1. An inertial drive actuator comprising: a shift unit that
generates a small shift in a first direction and in a second
direction opposite to the first direction; a vibration base plate
that moves to and fro with the small shift of the shift unit; and a
mover disposed on a flat surface of the vibration base plate and
having a first magnetic field generating unit, wherein the mover
comprises a first yoke that guides magnetic flux generated by the
first magnetic field generating unit in such a way that the
magnetic flux generated by the first magnetic field generating unit
concentrates on a surface of the mover facing the vibration base
plate with respect to both S and N poles, the inertial drive
actuator further comprises a second yoke disposed on a side of the
vibration base plate facing away from the mover, and a frictional
force acting between the mover and the vibration base plate is
controlled by controlling a magnetic field generated by the first
magnetic field generating unit to drive the mover; wherein the
first yoke includes a cavity and the first yoke further having a
member disposed within the cavity; the member includes a first
portion extending from the first yoke towards the vibration base
plate; and the member has a T-shape in cross-section.
2. The inertial drive actuator according to claim 1, further
comprising a second magnetic field generating unit that generates a
magnetic field relative to the magnetic field generated by the
first magnetic field generating unit so that a magnetic attractive
force or a magnetic repulsive force acts in the direction in which
the mover is opposed to the vibration base plate, wherein the
second yoke is located near the second magnetic field generating
unit to guide the magnetic flux generated by the second magnetic
field generating unit in such a way that the magnetic flux
generated by the second magnetic field generating unit concentrates
on its stator side surface with respect to both N and S poles, and
a frictional force acting between the mover and the vibration base
plate is controlled by controlling the magnetic field generated by
the first magnetic field generating unit and the magnetic field
generated by the second magnetic field generating unit to drive the
mover.
3. The inertial drive actuator according to claim 1, wherein the
first magnetic field generating unit comprises a magnet coil.
4. The inertial drive actuator according to claim 2, wherein the
second magnetic field generating unit comprises a permanent
magnet.
5. The inertial drive actuator according to claim 1, wherein the
shift unit comprises a piezoelectric element.
6. The inertial drive actuator according to claim 1, wherein the
vibration base plate is made of a non-magnetic material.
7. The inertial drive actuator according to claim 1, wherein the
vibration base plate comprises a non-magnetic part and a magnetic
part.
8. The inertial drive actuator according to claim 2, wherein at
least a part of the vibration base plate comprises the second
magnetic field generating unit.
9. The inertial drive actuator according to claim 1, wherein the
vibration base plate also functions as the second yoke.
10. The inertial drive actuator according to claim 1, wherein the
first magnetic field generating unit comprises a magnetic coil and
a permanent magnet.
11. The inertial drive actuator according to claim 1, wherein the
first magnetic field generating unit comprises a magnetic coil
wound around the member.
12. The inertial drive actuator according to claim 1, wherein at
least a portion of the first yoke has a L-shape in
cross-section.
13. An inertial drive actuator comprising: a shift unit that
generates a small shift in a first direction and in a second
direction opposite to the first direction; a vibration base plate
that moves to and fro with the small shift of the shift unit; and a
mover disposed on a first surface of the vibration base plate, the
vibration base plate having a first magnetic field generating unit,
wherein the mover comprises a first yoke disposed on the first
surface, the first yoke guides magnetic flux generated by the first
magnetic field generating unit in such a way that the magnetic flux
generated by the first magnetic field generating unit concentrates
on a surface of the mover facing the vibration base plate with
respect to both S and N poles, the inertial drive actuator further
comprises a second yoke opposed to the first surface such that at
least one end portion of each of the first and second yokes oppose
each other, and a frictional force acting between the mover and the
vibration base plate is controlled by controlling a magnetic field
generated by the first magnetic field generating unit to drive the
mover; wherein the first yoke includes a cavity and the first yoke
further having a member disposed within the cavity; the member
includes a first portion extending from the first yoke towards the
vibration base plate; and the member has a T-shape in
cross-section.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an inertial drive actuator that
causes a movable member to move in a predetermined direction.
Description of the Related Art
There is a known actuator in which saw-tooth pulses are supplied to
an electromechanical transducer coupled with a drive shaft to shift
the drive shaft in the axial direction, thereby moving a movable
member frictionally coupled with the drive shaft in the axial
direction. (Such an actuator will be hereinafter referred to as an
"impact drive actuator" or "inertial drive actuator".)
Such an impact drive actuator is disclosed in Japanese Patent
Application Laid-Open No. 2007-288828. FIG. 9A shows the
construction of the impact drive actuator. A vibration member 103
is inserted through holes provided in standing portions of a
support member 101 and movable in the axial direction of the
vibration member 103. One end of the vibration member 103 is fixed
to one end of a piezoelectric element 102, the other end of which
is fixed to the support member 101. With this construction, the
vibration member 103 vibrates in the axial direction with the
vibration of the piezoelectric element 102. A movable member 104
has two holes, through which the vibration member 103 is inserted.
A leaf spring 105 is attached to the movable member 104 from below.
A projection provided on the leaf spring 105 is pressed against the
vibration member 103. The pressure exerted by the leaf spring 105
brings the movable member 104 and the vibration member 103 into
frictional coupling with each other.
FIGS. 9B and 9C show waveforms of driving pulses for driving the
impact drive actuator. FIG. 9B shows a waveform of driving pulses
for moving the movable member 104 to the right, and FIG. 9C shows a
waveform of driving pulses for moving the movable member 104 to the
left. The operation principle of the impact drive actuator will be
described in the following with reference to these driving pulse
waveforms. In the following description, it is assumed that the
direction in which the piezoelectric element 102 expands is the
left, and the direction in which the piezoelectric element
contracts is the right.
When the movable member 104 is to be moved to the right, the
driving pulse waveform shown in FIG. 9B is used. The driving pulse
waveform has steep rise portions and gradual fall portions. The
steep rise portions of the driving pulse waveform cause the
piezoelectric element 102 to expand quickly. Because the vibration
member 103 is fixed to the piezoelectric element 102, the vibration
member 103 moves to the left at high speed with the quick expansion
of the piezoelectric element 102. During that time, the inertia of
the movable member 104 overcomes the frictional coupling force
between it and the vibration member 103 (i.e. frictional force
between the vibration member 103 and the movable member 104 pressed
against it by the leaf spring 105), and therefore the movable
member 104 does not move to the left but stays at its position.
The gradual fall portions of the driving pulse waveform causes the
piezoelectric element 102 to contract slowly. Then, the vibration
member 103 slowly moves to the right with the slow contraction of
the piezoelectric element 102. During that time, the inertia of the
movable member 104 cannot overcome the frictional coupling force
between it and the vibration member 103, and therefore the movable
member 104 moves to the right with the movement of the vibration
member 103.
On the other hand, when the movable member 104 is to be moved to
the left, the driving pulse waveform shown in FIG. 9C is used. The
driving pulse waveform has gradual rise portions and steep fall
portions. The gradual rise portions of the driving pulse waveform
cause the piezoelectric element 102 to expand slowly. Then, the
vibration member 103 moves slowly to the left with the slow
expansion of the piezoelectric element 102. During this time, the
inertia of the movable member 104 cannot overcome the frictional
coupling force between it and the vibration member 103, and
therefore the movable member 104 moves to the left with the
movement of the vibration member 103.
On the other hand, during the steep rise portions of the driving
pulse waveform, the inertia of the movable member 104 overcomes the
frictional coupling force between it and the vibration member 103,
as with the case described above with reference to FIG. 9B, and
therefore the movable member 104 does not move to the right but
stays at its position.
Since the vibration member 103 is always pressed by the leaf spring
105, the movable member 104 is frictionally supported by the
vibration member 103. In consequence, when the movable member 104
is stationary, its position is maintained.
As described above, the impact drive actuator utilizes the
frictional coupling of the movable member 104 and the vibration
member 103 provided by the leaf spring 105 and the inertia, and it
can move the movable member 104 using driving pulse waveforms shown
in FIGS. 9B and 9C.
The impact drive actuator disclosed in Japanese Patent Application
Laid-Open No. 2007-288828 uses a leaf spring to provide a
frictional force between the vibration member 103 and the movable
member 104.
SUMMARY OF THE INVENTION
An inertial drive actuator according to the present invention
comprises a shift unit that generates a small shift in a first
direction and in a second direction opposite to the first
direction, a vibration base plate that moves to and fro with the
small shift of the shift unit, and a mover disposed on a flat
surface of the vibration base plate and having a first magnetic
field generating unit, wherein the mover comprises a first yoke
that guides magnetic flux generated by the first magnetic field
generating unit in such a way that the magnetic flux generated by
the first magnetic field generating unit concentrates on a surface
of the mover facing the vibration base plate with respect to both S
and N poles, the inertial drive actuator further comprises a second
yoke disposed on a side of the vibration base plate facing away
from the mover, and a frictional force acting between the mover and
the vibration base plate is controlled by controlling a magnetic
field generated by the first magnetic field generating unit to
drive the mover.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1A and 1B show the structure of an inertial drive actuator
according to a first embodiment, where FIG. 1A is a side view, and
FIG. 1B is a cross sectional view;
FIG. 2 is a cross sectional view similar to FIG. 1B, showing the
structure of an inertial drive actuator according to a second
embodiment;
FIGS. 3A and 3B show the structure of an inertial drive actuator
according to a third embodiment, where FIG. 3A is a side view, and
FIG. 3B is a cross sectional view;
FIG. 4 is a cross sectional view similar to FIG. 1B, showing the
structure of an inertial drive actuator according to a fourth
embodiment;
FIG. 5 is a cross sectional view similar to FIG. 1B, showing the
structure of an inertial drive actuator according to a fourth
embodiment;
FIG. 6 illustrates a method of driving in operating the inertial
drive actuator 100 according to the first embodiment;
FIG. 7 is a side view showing the structure of an inertial drive
actuator according to a sixth embodiment;
FIGS. 8A, 8B, and 8C illustrate a method of driving in operating
the inertial drive actuator according to the sixth embodiment;
FIGS. 9A, 9B, and 9C show an impact drive actuator according to a
prior art, where FIG. 9A shows the construction of the actuator,
FIG. 9B shows a waveform of driving pulses for shifting the mover
to the right, and FIG. 9C shows a waveform of driving pulses for
shifting the mover to the left.
DETAILED DESCRIPTION OF THE INVENTION
The construction, operations, and advantages of inertial drive
actuators according to several embodiments will be described. It
should be understood that the present invention is not limited by
the embodiments. Although a lot of specific details will be
described in the following description of the embodiments for the
purpose of illustration, various modifications and changes can be
made to the details without departing from the scope of the
invention. The illustrative embodiments of the invention will be
described in the following without any intension of invalidating
the generality of or imposing any limitations on the claimed
invention.
(First Embodiment)
FIGS. 1A, 1B, and 1C show an inertial drive actuator according to a
first embodiment. FIG. 1A is a side view of the inertial drive
actuator, and FIG. 1B is a cross sectional view taken along line
A-A in FIG. 1A.
The inertial drive actuator 100 according to the first embodiment
includes a piezoelectric element (shift unit) 3, a vibration base
plate 4, a mover 10, and a stator 20. The piezoelectric element 3
and the vibration base plate 4 are disposed on top of the stator
20, and the mover 10 is disposed on top of the vibration base plate
4.
The mover 10 includes a coil 11 (first magnetic field generating
unit) and a first yoke 12a. The first yoke (magnetic flux guide
member) 12a is a grooved member having a groove (or recess), which
is partitioned by a T-shaped member at its center. The coil 11 is
wound in a cylindrical shape around a coil core surrounding the
T-shaped member. Wiring L for supplying electric current to the
coil 11 extends out of the first yoke 12a. The grooved member and
the T-shaped member are connected with each other.
The piezoelectric element 3 and the vibration base plate 4 are both
plate-like members. The vibration base plate 4 is made of a
non-magnetic material. One end of the piezoelectric member 3 and
one end of the vibration base plate 4 are mechanically connected.
Their connection is not limited to mechanical connection, but they
may be adhered to each other. The piezoelectric element 3 and the
vibration base plate 4 are disposed on top of the stator 20. The
piezoelectric member 3 generates a small shift or displacement,
which causes the vibration base plate 4 to move to and fro.
The stator 20 includes a permanent magnet 21 (second magnetic field
generating unit) and a second yoke (magnetic flux guide member)
22a. The permanent magnet 21 is a cuboid component having an N-pole
on one side and an S-pole on the other side. The second yoke 22a is
a box-like component. The permanent magnet 21 is disposed inside
the second yoke 22a with its N-pole side facing upward. The
permanent magnet 21 is fixed on the bottom of the second yoke
22a.
Now, the operation of the inertial drive actuator 100 will be
described. The principle of driving (or method of driving) will be
described with reference to FIG. 6. Current is supplied to the coil
11 in such a way that the S-pole is generated in the downward
direction in the drawing. The yoke 12a is arranged on both sides of
the coil 11. Therefore, the first yoke 12a can prevent magnetic
flux generated by the coil 11 from leaking to the outside. In
consequence, the S-pole concentrates to the center P1 of the lower
part of the first yoke 12a, and the N-pole concentrates to both
ends P2 of the lower part of the first yoke 12a.
On the other hand, in the stator 20 opposed to the first yoke 12a,
the permanent magnet 21 is surrounded by the second yoke 22a.
Therefore, the second yoke 22a can prevent magnetic flux generated
by the permanent magnet 21 from leaking to the outside. In
consequence, the N-pole concentrates to the upper part of the
permanent magnet 21, and the S-pole concentrates to both ends P3 of
the upper part of the second yoke 22a.
As described above, in the inertial drive actuator 100 according to
this embodiment, magnetic flux is prevented from leaking out of the
mover 10 or out of the stator 20, whereby the S-pole and the N-pole
can be concentrated to predetermined regions. Consequently,
magnetic attractive force can be generated efficiently in the
downward direction in the drawing between the mover 10 and the
stator 20.
Conversely, when current is supplied to the coil 11 in such away
that the S-pole is generated in the upward direction in the
drawing, the N-pole concentrates to the center P1 of the lower part
of the first yoke 12a, and the S-pole concentrates to both ends P2
of the lower part of the first yoke 12a. On the other hand, in the
stator 20 opposed to the first yoke 12a, the N-pole concentrates to
the upper part of the permanent magnet 21, and the S-pole
concentrates to both ends P3 of the upper part of the second yoke
22a. Consequently, magnetic repulsive force can be generated
efficiently in the upward direction in the drawing between the
mover 10 and the stator 20.
The magnitude of the normal force acting between the mover 10 and
the vibration base plate 4 (or the magnetic attractive or repulsive
force acting between the mover 10 and the stator 20) can be varied
by varying the amount of current supplied to the coil 11. This
enables controlling the frictional force between the mover 10 and
the vibration base plate 4.
As described above, the inertial actuator 100 according to this
embodiment utilizes a magnetic force to move or drive the mover 10.
Thus, the inertial drive actuator 100 according to this embodiment
is free from an elastic member that might wear by driving.
Therefore, moving or driving the mover 10 does not lead to wearing.
Consequently, it is possible to move or drive the mover 10 (i.e. to
move it to a desired position and to keep it at a desired position)
stably for a long period of time. Moreover, the use of the yoke in
the inertial drive actuator 100 according to this embodiment
enables prevention of the leakage of magnetic flux to the outside.
Consequently, the magnetic attractive force and the magnetic
repulsive force can be generated efficiently. Therefore, the mover
10 can be moved or driven efficiently, while the inertial drive
actuator is simple in structure and can be made at low cost.
(Second Embodiment)
Next, an inertial drive actuator according to a second embodiment
will be described. The components same as those in the first
embodiment will be denoted by the same reference characters to
eliminate redundant descriptions.
FIG. 2 is a cross sectional view of the inertial drive actuator
similar to FIG. 1B.
The inertial drive actuator 200 according to the second embodiment
includes a piezoelectric element 3 (not shown in FIG. 2), a
vibration base plate 4, a mover 10, and a stator 20. The
piezoelectric element 3 and the vibration base plate 4 are disposed
on top of the stator 20, and the mover 10 is disposed on top of the
vibration base plate 4.
In the mover 10 of the inertial drive actuator 100 according to the
first embodiment, the first yoke 12a covers two portions of the
coil 11. In contrast, in the mover 10 of the inertial drive
actuator 200 according to this embodiment, the first yoke 12b
covers only one of the two portions of the coil 11. In other words,
while in the inertial drive actuator 100 according to the first
embodiment, the first yoke 12a is provided for two side portions of
the coil 11, in the inertial drive actuator 200 according to this
embodiment, the first yoke 12b is provided only for one side
portion of the coil 11.
Referring to the stator 20, while in the inertial drive actuator
100 according to the first embodiment the second yoke 22a is
provided on both sides of the permanent magnet 21, in the inertial
drive actuator 200 according to this embodiment the second yoke 22b
is provided on only one side of the permanent magnet 21.
As described above, the inertial drive actuator 200 according to
this embodiment partly differs in structure from the inertial drive
actuator 100 according to the first embodiment. Nevertheless, the
inertial drive actuator 200 according to this embodiment has
advantages in magnetic attractive and repulsive forces
substantially the same as the inertial drive actuator 100 according
to the first embodiment. In the inertial drive actuator 200
according to this embodiment, the first yoke 12b and the second
yoke 22b are disposed on only one side of the coil 11 and the
permanent magnet 21. Therefore, if the overall size of the inertial
drive actuator is the same as the first embodiment, the number of
turns of the coil can be made larger in this embodiment than in the
first embodiment. Consequently, if the current supplied to the coil
11 is the same as the first embodiment, higher magnetic flux
density can be achieved, leading to increased magnetic attractive
and repulsive forces.
(Third Embodiment)
Next, an inertial drive actuator according to a third embodiment
will be described.
FIG. 3A is a side view of the inertial drive actuator, and FIG. 3B
is a cross sectional view taken along line A-A in FIG. 3A. The
components same as those in the inertial drive actuator according
to the first embodiment will be denoted by the same reference
characters to eliminate descriptions thereof. Wiring is not
illustrated in these drawings.
The inertial drive actuator 300 according to the third embodiment
includes a piezoelectric element 3, a mover 10, and a vibration
base plate 40. The mover 10 is disposed on top of the vibration
base plate 40. One end of the piezoelectric member 3 and one end of
the vibration base plate are mechanically connected.
The mover 10 includes a coil 11 and a first yoke 12c. The structure
of the mover 10 is the same as that of the mover 10 in the first
embodiment and will not be described further. The mover 10 in this
embodiment plays the same role as the mover 10 in the first
embodiment. The vibration base plate 40 includes a permanent magnet
40 and a second yoke 22c. The vibration base plate 40 plays the
same role as the stator 20 in the first embodiment as well as the
vibration base plate 4.
The inertial drive actuator 300 according to this embodiment
includes components having the same functions as components in the
inertial drive actuator 100 according to the first embodiment, and
has the same advantages as the inertial drive actuator 100
according to the first embodiment accordingly. Since the vibration
base plate 40 in the inertial drive actuator 300 according to this
embodiment plays multiple roles, reduction in the size of the
actuator can be achieved.
(Fourth Embodiment)
Next, an inertial drive actuator according to a fourth embodiment
will be described.
FIG. 4 is a cross sectional view of the inertial drive actuator
similar to FIG. 1B. The components same as those in the first
embodiment will be denoted by the same reference characters to
eliminate descriptions thereof.
The inertial drive actuator 400 according to the fourth embodiment
includes a piezoelectric element 3 (not shown in FIG. 4), a
vibration base plate 4, a mover 10, and a stator 20. The
piezoelectric element 3 and the vibration base plate 4 are disposed
on top of the stator 20, and the mover 10 is disposed on top of the
vibration base plate 4.
The mover 10 includes a coil 11, a first yoke 12d, and a permanent
magnet 13. The first yoke 12d is a grooved member having a groove,
which is partitioned by a T-shaped member at its center. The coil
11 is wound in a cylindrical shape around a coil core surrounding
the T-shaped member. The grooved member and the T-shaped member are
separated from each other, and the permanent magnet 13 is arranged
between them. The permanent magnet 13 is disposed with its N-pole
facing the T-shaped member. The stator 20 has a second yoke
22d.
This embodiment differs from the first embodiment in that it lacks
the permanent magnet 21 (second magnetic field generating unit) in
the first embodiment.
In the inertial drive actuator 400 having the above-described
construction, when current is supplied to the coil 11, for example,
in such a way that the N-pole is generated in the downward
direction in the drawing. Then, the N-pole concentrates to the
center of the lower part of the first yoke 12d, and the S-pole
concentrates to both ends of the lower part of the first yoke
12d.
As to the magnetic flux generated by the permanent magnet 13 also,
the N-pole concentrates to the center of the lower part of the
first yoke 12d, and the S-pole concentrates to both ends of the
lower part of the first yoke 12d. In the stator 20 opposed to the
first yoke 12d, magnetization in the reverse polarity is induced in
the second yoke 22d. Specifically, an S-pole is induced at the
center of the second yoke 22d, and N-poles are induced at both ends
of the second yoke 22d. Consequently, a magnetic attractive force
stronger than that in the case where no current is supplied to the
coil 11 acts on the mover 10 in the downward direction in the
drawing.
On the other hand, when current is supplied to the coil 11 in such
a way that the N-pole concentrates to the upward direction in the
drawing, a magnetic attractive force weaker than that in the case
where no current is supplied to the coil 11 is generated. The
magnitude of the normal force acting between the mover 10 and the
vibration base plate 4 can be varied by varying the current
supplied to the coil 11. This enables controlling the frictional
force between the mover 10 and the vibration base plate 4.
As described above, in the inertial drive actuator 400 according to
this embodiment, a magnetic force is used in moving or driving the
mover 10. Thus, the inertial drive actuator 400 according to this
embodiment is free from an elastic member that might wear by
driving. Therefore, moving or driving the mover 10 does not lead to
wearing. Consequently, it is possible to move or drive the mover 10
(i.e. to move it to a desired position and keep it at a desired
position) stably for a long period of time. Moreover, the use of
the yoke in the inertial drive actuator 400 according to this
embodiment enables prevention of the leakage of magnetic flux to
the outside. Consequently, the magnetic attractive force and the
magnetic repulsive force can be generated efficiently. Therefore,
the mover 10 can be moved or driven efficiently.
(Fifth Embodiment)
Next, an inertial drive actuator according to a fifth embodiment
will be described. FIG. 5 is a cross sectional view of the inertial
drive actuator similar to FIG. 1B. The components same as those in
the first embodiment will be denoted by the same reference
characters and will not be described further.
The inertial drive actuator 500 according to the fifth embodiment
includes a piezoelectric element 3 (not shown in FIG. 5), a
vibration base plate 4, a mover 10, and a stator 20. The
piezoelectric element 3 and the vibration base plate 4 are disposed
on top of the stator 20, and the mover 10 is disposed on top of the
vibration base plate 4.
The inertial drive actuator 500 according to the fifth embodiment
differs from the inertial drive actuator 100 according to the first
embodiment in the structure of the vibration base plate. While the
vibration base plate 4 in the first embodiment is made only of
non-magnetic material, the vibration base plate 4 in this
embodiment includes a magnetic part 41 and a non-magnetic part 42.
The magnetic part functions as a yoke. The magnetic part 41
includes three separate parts, which are arranged at the center of
the vibration base plate 4 and on both sides of the center. The
center magnetic part 41 is substantially opposed to the T-shaped
member (of the first yoke 12e). The side magnetic parts 41 are
substantially opposed to the edges of the grooved member (of the
first yoke 12e).
In the inertial drive actuator 500 according to this embodiment,
magnetic flux guided by the first yoke 12e of the mover 10 and
magnetic flux guided by the second yoke 22e of the stator 20 flow
through the magnetic parts 41 in the vibration base plate 4.
Therefore, better prevention of leakage of magnetic flux can be
achieved advantageously. In particular, leakage of magnetic flux to
the outside in the region near the lower edges of the first yoke
12e and the upper edges of the second yoke 22e can be reduced
greatly by virtue of the two side magnetic parts 41 existing
between them.
Next, the method of driving in the inertial drive actuator
according to the embodiments will be described. FIG. 6 illustrates
the method of driving in an inertial drive actuator, e.g. the
inertial drive actuator 100 according to the first embodiment. In
FIG. 6, the horizontal axis represents time, and the vertical axis
represents shift of the piezoelectric element 3, where expanding
shifts of the piezoelectric element 3 to the left in FIG. 1A are
expressed by positive values.
During the time period from time 0 to time A, the piezoelectric
element 3 is expanding. During this period, current is supplied to
the coil 11 in such away that the S-pole is generated in the
downward direction in the drawing. Then, the magnetic attractive
force acting on the mover 10 in the direction toward the vibration
base plate 4 increases. In consequence, the friction between the
mover 10 and the vibration base plate 4 increases. Consequently, as
the vibration base plate 4 moves to the left in the drawing with
the expansion of the piezoelectric member 3, the mover 10 moves to
the left in the drawing accordingly.
During the time period from time A to time B, the piezoelectric
element 3 is contracting. During this period, current supply to the
coil 11 is suspended. Then, no magnetic attractive force generated
by the coil 11 acts on the mover 10. In consequence, the frictional
force between the mover 10 and the vibration base plate 4
decreases. This means that the amount of slippage of the mover 10a
relative to the movement of the vibration base plate 4 increases.
Consequently, while the vibration base plate 4 moves to the right
in the drawing with the contraction of the piezoelectric element,
the mover 10 apparently stays stationary at the shifted position.
In this way, while the piezoelectric element 3 is contracting, the
mover 10 slips to the left relative to the vibration base plate 4,
which moves to the right in the drawing. Thus, the mover 10 shifts
to the left in the drawing during the time period from time 0 to
time B.
As the same operation is performed repeatedly in the time period
from time B to time C, the time period from time C to time D and so
on, the mover 10 moves or shifts to the left in the drawing. The
mover 10 can also be moved to the right in the drawing by reversing
the timing of current supply to the coil 11 shown in FIG. 6.
Specifically, the mover 10 is moved to the right in the drawing, by
supplying the coil 11 with current with which a magnetic repulsive
force acting between the mover 10 and the vibration base plate 4 is
generated instead of current with which a magnetic attractive force
acting between the mover 10 and the vibration base plate 4 is
generated, during the time period from time 0 to time A.
While in the above-described illustrative case, current supply is
suspended during the time period from time A to time B, the coil 11
may be supplied with current with which a magnetic repulsive force
acts between the mover 10 and the vibration base plate 4 during
this period. This also enables the mover 10 to move in the same
manner as described above.
(Sixth Embodiment)
Next, an inertial drive actuator according to a sixth embodiment
will be described.
FIG. 7 is a side view of the inertial drive actuator similar to
FIG. 1B. FIGS. 8A, 8B, and 8C illustrate a method of driving in the
inertial drive actuator 100 according to the sixth embodiment.
The inertial drive actuator according to the sixth embodiment has
two movers 10 like that in the inertial drive actuator 100 in the
first embodiment. Specifically, the inertial drive actuator 600
according to the sixth embodiment includes a piezoelectric element
3, a vibration base plate 4, a mover 10a, a mover 10b, and a stator
20. The piezoelectric element 3 and the vibration base plate 4 are
disposed on top of the stator 20, and the mover 10a and the mover
10b are disposed on top of the vibration base plate 4. Wiring is
not illustrated in FIG. 7.
The method of driving in the inertial drive actuator 600 will be
described. In FIGS. 8A, 8B, and 8C, the horizontal axis represents
time, and the vertical axis represents shift of the piezoelectric
element 3, where expanding shifts of the piezoelectric element 3 to
the left in FIG. 7 are expressed by positive values.
During the time period from time 0 to time A, the piezoelectric
element 3 is expanding. During this period, current is not supplied
to the coil 11 in the mover 10a. Then, no magnetic attractive force
acts on the mover 10a. Consequently, the mover 10a stays stationary
without changing its position. On the other hand, current is
supplied to the coil 11 in the mover 10b in such a way that the
S-pole is generated in the downward direction in the drawing. Then,
a magnetic attractive force acts on the mover 10b in the direction
toward the vibration base plate 4, as described above with
reference to FIG. 6. In consequence, the mover 10b moves to the
left in the drawing.
During the time period from time A to time B, the piezoelectric
element 3 is contracting. During this period, current is supplied
to the coil 11 in the mover 10a in such a way that the S-pole is
generated in the downward direction in the drawing. Then, a
magnetic attractive force acts on the mover 10a in the direction
toward the vibration base plate 4, as described above with
reference to FIG. 6. In consequence, the mover 10a moves to the
right in the drawing. On the other hand, current is not supplied to
the coil 11 in the mover 10b. Then, no magnetic attractive force
acts on the mover 10b. Consequently, the mover 10b stays stationary
without changing its position.
As described above, during the time period from time 0 to time A,
the mover 10a stays stationary, and the mover 10b moves to the left
in the drawing or toward the mover 10a. On the other hand, during
the time period from time A to time B, the mover 10a moves to the
right in the drawing or toward the mover 10b, and the mover 10b
stays stationary. Consequently, the mover 10a and the mover 10b can
be brought closer to each other. By performing the driving
operation during the time period from time 0 to time B repeatedly,
the mover 10a and the mover 10b can be brought further closer to
each other. Moreover, by changing the driving method, it is also
possible to move the mover 10a and the mover 10b in the same
direction or to move the mover 10a and the mover 10b away from each
other.
While a construction with two movers and a method of driving
thereof have been described by way of illustration with reference
to FIGS. 7, 8A, 8B, and 8C, more than two movers can be moved
independently from each other on the same vibration base plate
according to the same principle. Moreover, because the mover
includes a coil in all of the first to fifth embodiments, the
principle of driving illustrated in FIGS. 7, 8A, 8B, and 8C can be
applied to all the embodiments. Therefore, it is possible to move a
plurality of movers independently from each other on the same
vibration base plate in the inertial drive actuators according to
the embodiments.
Various modification can be made without departing from the essence
of the present invention.
As described above, the present invention can suitably be applied
to an inertial drive actuator capable of operating stably for a
long period of time, for example in moving a mover to a desired
position, stopping the mover at a desired position, and keeping the
mover stationary.
The present invention can provide an inertial drive actuator that
uses a magnetic force to reduce adverse effects of wearing etc. and
can move or drive a mover efficiently by using a yoke.
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